Bless your heart.... I have a beagle mix who has diabetes/cushings. One thing that my vet mentioned straight away is that she can sense our “pity” and will take advantage. She’s of average intelligence and so she was easier to put back into place but a springer is smarter and so you may have a little more of an issue.
The first thing that you can do is go to ceasar milans website. His understanding of dogs is complete.
With Chloe we essencially had to take her to boot camp. First the walks....always on a leash and the demand that she walks next to us, never pulling the leash or running ahead. It’s very frustrating to re-teach that and time consuming. I bet I stopped during a walk 30 times.
To assert your dominance you can use your body. When you walk into the door do not talk to her, touch her or look at her until she is in a submissive state. And one of the big ones that we do as dog lovers is reward bad behavior. Dont pet her and love on her to calm her down. That reinforces that behavior.
I hope that you get to keep her, I had to put my Golden down a few months ago and I’m still grieving. : (
Please go to Ceasars website...he has amazing advise for all of that behavior.